Using a key fob system to lock or unlock vehicle doors is convenient for a driver because the driver does not have to use an actual key to lock or unlock the vehicle doors. Also, the key fob system allows the driver to lock or unlock a rear hatch or truck and to remotely initiate a vehicle engine. Furthermore, the key fob system can be used to alert the driver to locate his vehicle by alarming sound or turning lights on and off. To broaden the range of applications of such a key fob system, recent trends have been to add greater range, to give them bi-directional capacity, and to add a display to indicate vehicle information. Since these control functions requires more energy and power, the current trend is to make the key fob battery rechargeable or larger, heavier and more expensive.